Xylene isomerization process and catalyst therefor

• US 9,266,794 B1
• Filed: 10/23/2015
• Issued: 02/23/2016
• Est. Priority Date: 08/31/2012
• Status: Active Grant

• Current Assignee: ExxonMobil Chemical Patents Inc. (Exxon Mobil Corporation)
• Original Assignee: ExxonMobil Chemical Patents Inc. (Exxon Mobil Corporation)
• Inventors: Ou, John Di-Yi, Luo, Shifang L., Jain, Surbhi
• Primary Examiner(s): Dang, Thuan D
• Application Number:
  US14/921,464
• Publication Number:
  US 20160039727A1
• Time in Patent Office: 123 Days
• Field of Search: 585/481
• US Class Current: 1/1
• CPC Class Codes: C07C 15/08 Xylenes
• CPC Class Codes: C07C 2529/40 of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11
• CPC Class Codes: C07C 5/2737 with crystalline alumino-silicates, e.g. molecular sieves
• CPC Class Codes: Y02P 20/52 using catalysts, e.g. selective catalysts

Abstract

The invention concerns a xylenes isomerization process for the production of equilibrium or near-equilibrium xylenes from a feedstream comprising phenol and/or styrene.

Claims

1. A process for the isomerization of a paraxylene-depleted aromatic hydrocarbon feedstream comprising styrene, wherein said isomerization of a paraxylene-depleted feedstream is conducted in the presence of a catalyst comprising HZSM-5, wherein said HZSM 5 is characterized by an average crystal size of <

0.1 micron and a SiO₂/Al₂O₃ molar ratio in the range of about 20-100, in a reactor at a temperature of less than 295°

C., and a pressure sufficient to maintain the xylenes in liquid phase to produce an isomerization product.

2. The process of claim 1, wherein said feedstream is characterized as containing styrene in the amount of 100 ppm or less.

3. The process of claim 1, wherein said feedstream is characterized as containing styrene in the amount of 50 ppm or less.

4. The process of claim 1, wherein said feedstream is characterized as containing styrene in the amount of 20 ppm or less.

5. The process of claim 1, further characterized in that said process is operated in a continuous mode with a feedstream containing low ppm levels of dissolved H₂ in the range of about 4 to 100 ppm.

6. The process of claim 1, further characterized in that said process is operated in a continuous mode with a feedstream containing low ppm levels of dissolved H₂ in the range of about 4 to 20 ppm.

7. The process of claim 1, further characterized in that said process is operated in a cyclic mode with an H₂-free feedstream, and further wherein said catalyst is periodically regenerated by a step including contacting said catalyst with an H₂-containing feedstream, wherein said H₂-free feedstream is characterized as containing less than 4 ppm dissolved H₂ and said H₂-containing feedstream is characterized as containing about 4 or more ppm dissolved H₂.

8. The process of claim 1, wherein said reactor is at a temperature of 260°

C. or less.

9. The process of claim 1, including a step of decreasing the amount of styrene upstream of said isomerization.

10. The process of claim 1, wherein said paraxylene-depleted feedstream is characterized as an aromatic hydrocarbon feedstream consisting essentially of a xylenes wherein the concentration of paraxylene is less than about 22 wt % relative to the total C8 aromatic hydrocarbons in said feedstream.

11. The process of claim 9, wherein said decreasing comprises:

treating a paraxylene-containing feedstream comprising styrene to reduce the amount of said styrene, wherein said treating comprises contact of said paraxylene-containing feedstream with a material selective for the reduction of styrene relative to phenol and paraxylene to produce a first product having a reduced concentration of styrene.

12. The process of claim 11, wherein said paraxylene-containing feedstream comprises paraxylene obtained from reformate, an alkylation reaction, imported paraxylene, and mixtures thereof.